1. Field of the Invention
The present invention relates to a joint structure of ceramics and metal and an intermediate insertion member used in this joint structure.
2. Description of Related Art
Nowadays, electrostatic chucks are being used to absorb and hold semiconductor wafers in transferring, light-exposing, film-forming such as CVD and sputtering, fine processing, washing, etching, dicing, etc. for semiconductor wafers. Dense ceramics are noted for substrates of such electrostatic chucks. Particularly, in the semiconductor producing apparatus, a halogen based corrosive gas such as CIF3, CF4, NF3 is often used as an etching gas. In order to rapidly heat and cool the semiconductor wafer while being held by such a substrate, the substrate of the electrostatic chuck is desired to have high heat conductivity. Further, it is desired that the substrate has such thermal shock resistance as not being destroyed by rapid temperature changes. Dense aluminum nitride and alumina have high corrosion resistance against the halogen based corrosion gas mentioned above.
In the field of the semiconductor producing apparatuses, susceptors in which built-in high frequency electrodes for generating plasma have been practically used. In the field of such high frequency electric power generating apparatuses, ceramics heaters in which a metal resistor is embedded in a substrate of aluminum nitride or alumina for controlling the temperature of a wafer in each process.
In these apparatuses, it is necessary that the metal electrode is em bedded in the ceramic substrate made of aluminum nitride or the like, and that the metal electrode is electrically coupled to an external electric power supply connector. However, a coupling portion for this purpose is exposed to a heat cycle between extreme high temperatures and low temperatures in an oxidative atmosphere and further in a corrosive gas atmosphere. Such a joint portion is desired to maintain high joining strength and excellent electric coupling performance for a long time period even under such a bad condition.
The present inventors have continuously studied the coupling structures as mentioned above. For example, Japanese Patent Laid-Open Publication No. 8-277,173 (JP-A-8-277,173) proposed that a mesh or net metal electrode is embedded in an AIN ceramics, while a part of the mesh or net metal electrode is exposed, ants the exposed mesh or net portion and the AIN ceramics are brazed to a tip face of the electric power supply connector. In the techniques mentioned above, the proposed brazing methods have a high corrosive resistance against the halogen based corrosive gas and its plasma. Moreover, the present inventors further proposed, in Japanese Patent Application No. 9-12,769 (U.S. Ser No. 09/013,045), a specific connector-metal electrode joint structure which can maintain high joining strength and excellent conductive performance even if high temperatures or heat cycle is applied thereto under an oxidative atmosphere. Further, the present inventors further proposed, in Japanese Patent Laid-Open Publication No. 11-12,053 (U.S. Ser. No. 09/095,157), a specific joining structure which can prevent an erosion of a metal embedded member in ceramics.
Under specific conditions in which the joint structure mentioned above are used, there are cases such that a heat cycle between high temperature and low temperature is repeated at a great number of times or for a long time, such that temperature differences, temperature descending rate and temperature ascending rate at respective heat cycles are extremely large, and such that a high mechanical stress is applied to a terminal. In these cases, there is a possibility such that cracks are generated in the brazing material at a joint portion between metal terminal and ceramics and a corrosive gas is penetrated through the brazing material. Moreover, there is also a possibility such that cracks are generated in respective ceramics members which constitute the joint portion.
An object of the present invention is to improve a durability against heat cycle and mechanical stress applied to a joint portion in a joint structure of a first member, having a substrate made of ceramics and a metal embedded member embedded in the substrate, in which a part of the metal embedded member is exposed to a joint surface of the first member, and a second member made of metal.
According to the invention, the above-discussed joint structure of the first member includes an intermediate insertion member interposed between the joint surface of the firsts member and the second member. A first joint layer joins the joint surface of the first member and the intermediate insertion member. A second joint layer joins the second member and the intermediate insertion member. The intermediate insertion member is made of a laminated member of a plurality of ceramics layers and at least one metal layer interposed between respective ceramics layers.
Moreover, according to the invention, an intermediate insertion member includes a laminated structure of a plurality of ceramics layers and at least one metal layer interposed between respective ceramics layers.